High-vacuum apparatus



June 11, 1929. o. SEITZ HIGH VACUUM APPARATUS Filed March .24, 1926 2Sheets-Sheet 1 June 1 9- o. SEITZ 1,716,507

HIGH VACUUM APPARATUS Filed March 24, 1926 2 Sheets-Sheet 2 PatentedJune l1, 1929.

UNITED STATES PATENT 0 FFICE.

OSKAR snrrz, or BAnEmswnzEnLANn, ASSIGNOR roAKaimNerisELLscHAFr BROWNBOVERI & cm, or BADEN, SWITZERLAND, A JOINT-STOCK COMPANY or swnZERLAND.

' HIGH-VACUUM APPARATUS;

Application filed March 24, 1926, Serial No. 97,071, and in GermanyMarch 27, 1925.

This invention relates to apparatus for producing high vacua,particularly to the sort of apparatus employing a plurality of vacuumpumps in series.

The general object of the invention is the provision of apparatusrequiring a minimum of moving parts and which will be certain inoperation, particularly throughout extended periods, or for intermittentservice.

Another. object is the provision of such apparatus particularly adaptedto automatic control, that is, to be automatically started and stoppedin accordance with the demands of the evacuateddevice. 1

Further and other objects of the invention will beindicated or pointedout hereinafter, or will'be obvious to one skilled in the art upon anunderstanding of the invention.

In the drawings forming a part of this specification I show indiagrammatic fashion certain forms of apparatus embodying the invention,but it is to be understood that the invention as claimed is not limitedto these particular structural forms.

In the said drawings,

Fig. 1 is a sectional elevation of a vacuum pump,

Fig. 2 is a similar-sectional elevation of a modified form,

v Fig. 3 is an elevational view, with part in section, illustrating theassociated connection of pumps in a two-stage assembly.

Referringfirst to the embodimentillus; trated in Fig. 1, let it beunderstood that the character a designates a mercury vapour generatingreceptacle provided with a heating element a, by which themercurycontained in the receptacle 0. may be heated to boiling for theproduction of mercury vapour under pressure in the receptacle. From thetop of the receptacle a leads a restricted discharge tube 1) terminatingin the ejection nozzle 0 which discharges in the contracting throat ofthe compression nozzle d. The compression nozzle cl comprises a tubularconvergent front portion or combining tube merginginto the aforesaidthroat, and a tubular divergent rear portion or deli-very tube openinginto the condensing chamber e. The inlet a for the gas that is tobepumped is at the wide front end of thefcombining tube, back of theopening of .the ejection nozzle.

The compression nozzle d and condensing chamber 6 are cooled bycirculation about them of a cooling fluid within the jacket J. Thecondensing chamber 6 has an outlet at its top through. the bafiied tubef which discharges into a trap or separator at g, which contains aliquid capable of condensing mer cury vapour and adapted to pass airoutwardly to the discharge hood [1. opening to,

the atmosphere. The separator is provided with asuitable connection anddrain cock 5 whereby mercury contained in the seal may be drawn off.From the bottom of the condensing chamber 6 a return'pipe I: leads tothe receptacle a, and from the closed lower end of the nozzle 03 anotherreturn pipe 70 leads to the receptacle a. These return pipes are ofsyphonic nature and afford seals preventingpassage of air through thereceptacle a. The pipe is must be of suflicient length to afford anadequate head p to retain the pressure difference between the low vacuumpressure in-nozzle d and the pressure in receptacle a. 1

In operation of the device the mercury vapourgenerated in a is forciblyejected through the vapor nozzlev a entraining with it the air in thesurrounding combining tube and compressing it inthe throat of the nozzle0?, wherein it is cooled by the surrounding cooling'fluid, anddischarged into the condensing chamber e at something in excess ofatmospheric pressure. In the condensing chamber 6 the greater part ofthe mercury vapour is condensed, and'returns to receptacle a throughpipelc. The compressed air leaves through pipe 7 passing through the.

seal of the separator g and gasses to atmosphere through the head It. hecooling liquid is introduced through the pipe L and finds outlet throughthe pipe m.

In the embodiment'illustrated in Fig. 2 the same elements are employed,but the direction of operation is reversed. In this form the tube 6 isextended up to the top of the device whereit discharges into the nozzle0 in such ,relationship that after discharge from b the direction of themercury yapouiis reversed and it is emitted from the nozzle in thedownward direction in the v compression nozzle 03. The latter leads tothe condensing chamber-e in which the mercury'vapour is condensed andreturns to re-' the features which make them suitable for.

operation against a .large pressure head, permitting their utilizationin combination with mercury-vapor h1gh-vacuum pumps,

thereby elminating rotary vacuum pumps used for creating a preliminaryvacuum for the high vacuum pumps.

In Fig. 3 is illustrated such two-stage ar rangement in which Idesignates the high vacuum pump having its inlet at 10 from theevacuated chamber and its air outlet at 11, the air being conductedthrough thepipe 12. to the vessel 14 which contains the mercury-foreffecting a barometric seal between the pipe 12 and the pipe 15 leadingto the air inlet 11' of the preliminary or leading air pump II, hereshown as the form illustrated in Fig. 2. In the pump I the air is raised,to a pressure of some 10 or 20 mm. mercury, and, entering the leadingpump II at that pressure is raised to a pressure permitting itsdischarge to atmosphere. Fig. 3 also shows the arrangement for circulating fluid. The fluid is introduced first to the cooling jacket of thehigh vacuum pump,.I.at 16, and leaves the same at 17, whence it isconducted-to the inlet 1 of the leading pump II, from which it is.dischar ed at m.

With the arrangement illustrated some degree of vacuum is alwaysmaintained in the high vacuum pump I. Consequently, upon the starting ofthe apparatus or the energizing of the heating elements in the twopumps, the mercury in the high vacuum pump I will boil first.Accordingly, as soon as the valve controlling connection between thereceivers and the high vacuum pump I =1s opened, which is accomplishedupon the starting of the leading pump II, the high vacuum pump, which isalready working, at

once commences to raise the vacuum in the though'it maybe of othersuitable kind. The apparatus possesses distinct advantages in itsfreedom from mechanical complications such as necessarily are involvedin pumps having moving parts which have to be actuated from externalsources.

What I claim is:

1. In vacuum apparatus, the combination of a primary vapor condensationhigh vacuum pump and a secondary vapor condensation vacuum pumpoperating in series with the same, said secondary pump being arranged tomaintain the primary pump under a negative pressure, and means forcirculating vapor condensing cooling fluid through said pumps in series,said cooling fluid passing in the direction from the primary pump to thesecondary pump.

2. Vacuum apparatus, in combination, a primary high vacuum pump of thediffusion type and a secondary pump connected to the exhaust oi? theprimary pump, said secondary pump comprising means for producing avapour jet arranged to compress the gas received from the primary pumpto super- ZLtHlOSPllGllC pressure.

3. Vacuum apparatus comprising, in combination, a primary Vacuum pump ofthe mercury vapour jet type, a secondary pump in series with the primarypump, said sec ondary pump discharging to atmosphere, and auni-direction seal between the pumps permitting flow of gas from theprimary to the secondary pump only.

4;. Vacuum apparatus comprising, in combination, a primary mercury vaporhigh vacuum pump, a secondary mercury vapor pump in series with theprimary pump for compressing the gas received from said primary pump tosuper-atmospheric pressure, a seal for the discharge of the secondarypump to prevent escape of mercury vapor from said pump, and auni-direction seal between the primary and secondary pumps permittinggas flow in the direction to the secondary pump only.

5. Vacuum apparatus comprising, in combination, a primary high vacuumpump of the mercury vapour type, a secondary pump in series therewith,said. secondary pump being of the mercury vapour jet type, and means forcirculating a vaporcondensing cooling medium through said pumps inseries.

6. Vacuum apparatus, comprising in combination, a compression nozzlehaving a contracted throat, .a condensing chamber into which said nozzledischarges, said condensing chamber having air outlet through a mercuryvapor seal, an ejector nozzle discharging through the compression nozzletowards the condensing chamber, a mercury vapour generator supplying.said ejector nozzle, a conduit for return of condensate from thecondensing chamber to the gen-- compression nozzle opening into thecondensing chamber, an ejector nozzle discharging through thecompression nozzle, a mercury vapor generator supplying the ejectornozzle, means for cooling the condensing chamber, a conduit :forreturning condensate from said chamber to the generator, and abarometric seal in said conduit.

8. A vapor jet vacuum pump comprising a boiler for generating vapor atsubstantially super-atmospheric pressure, a vapor discharge nozzleextending from said boiler, a compression nozzle having a convergincombining tube, a throat at the narrow en of said tube, a discharge tubeextending from said throat on the other side of said combining tube,said vapor discharge nozzle extending into said combining tube openingtoward said throat, a condensing chamber associated with said dischargetube, a gas inlet opening into said combining tube back of said nozzle,a gas discharge opening in said condensing chamber, means for cool pordischarge type, one of said pumps constituting the primary unit andbeing arranged for impelling gas from a relatively high vacuum against arelatively low pressure head, the other of said pumps constituting thesecondary unit and being arranged to impel the exhaust from the pri-'mary unit for discharge under atmospheric pressure conditions, adistinct mercury boiler for the primary unit, a distinctmercury boilerfor the sescondary unit, means for maintaining a pressure differencebetween the two serially-connected pumps under absence of mercury vaporaction, said means permittinggas flow in the direction from the lowpressure inlet toward the at-- mosphere only, and means forsubstantially simultaneously initiating the heating of the boilers saidtwo pumps.

10. In vacuum apparatus, a vapour generator, a chamber disposed aboveand communicating with said generator and being operable to receive andeffect condensation of the vapour supplied thereby, and, a trapproviding a vapour-condensate return from said chamber to said generatorand comprising legs disposed below thenormal level of the operatingliquid in said generator, one of said legs being connected to saidchamber, the other of said legs being connected to said generator atsubstantially such normal level.

In testimony whereof I have hereunto subscribed my name at Zurich,Switzerland, on the 15th day of February, A. D. 1926.

osKAR SEITZ.

